S-Adenosyl-L-methionine (AdoMet) dependent transmethylation reactions have been implicated in a variety of biological processes related to vital growth and replication, vital transformation of cells, growth of malignant cells, and processes such as chemotaxis and secretion [See P. M. Ueland, Pharm. Reviews, 34, 223 (1982)]. In general, these transmethylation reactions are catalyzed by various transmethylases which utilize AdoMet as a methyl-donor substrate in the methylation of a number of methyl-acceptor substrates such as catechols; norepinephrine; histamine; serotonin; tryptamine; membrane phospholipids; lysyl, arginyl, histidyl, aspartyl, glutamyl, and carboxyl groups of certain proteins; tRNA and mRNA; and DNA. These various transmethylases produce S-Adenosine-L-Homocysteine (AdoHcy) as a byproduct upon transfer of a methyl group from AdoMet to the appropriate methyl-acceptor substrate.
AdoHcy has been shown to be a potent feed-back inhibitor of the AdoMet-dependent transmethylation reactions. This feed-back inhibition of the transmethylases is controlled by the biodegradation of AdoHcy by S-Adenosyl-L-Homocysteine Hydrolase which provides a homeostatic control on the tissue levels of AdoHcy. The activity of S-Adenosyl-L-Homocysteine Hydrolase is generally considered by those skilled in the art to play an important role in regulating the tissue levels of AdoHcy and thereby controlling the activity of the AdoMet dependent transmethylation reactions.
The compounds of the present invention are inhibitors of S-Adenosyl-L-Homocysteine Hydrolase. These compounds therefore inhibit the naturally-occurring biodegradation of AdoHcy and result in elevated tissue levels of AdoHcy. Elevated levels of AdoHcy in turn provide an endogenous feed-back inhibition of various AdoMet dependent transmethylation reactions which are associated with biological processes related to viral growth and replication, viral transformation of cells, growth of malignant cells, and processes such as chemotaxis and secretion. The compounds of the present invention are therefore useful as inhibitors of these biological processes and useful in an end use application as therapeutic agents in the treatment of patients afflicted with various pathological conditions in which these processes are implicated, such as, viral infections and neoplastic disease states.